Metallic taste may result from a combination of activation of existing taste receptor lines rather than a dedicated metallic taste receptor.

“And is there really a receptor for metallic taste or it's nothing but this magical combination of the activation of the existing lines, think of it as lines of information, just separate lines, like the keys of a piano. Sweet sour bitter salt umami you play the key and you activate a one chord. And that one chord in the case of a piano leads to a note, you know a tune and in the case of taste leads to an action and a behavior, but you play many of them together. And something emerges that it's different than any one of the pieces. And it's possible that metallic, for example, represents the combination of the activity just in the right ratio makes of these other lines.”